The invention relates to the manufacture of repair material. In particular, the invention relates to the manufacture of repair material from alloys that are difficult to mechanically deform.
Turbine components, such as blades, nozzles, vanes, airfoils, tips and the like (hereinafter "turbine components") are frequently formed from superalloys, for example, nickel-based superalloys, that have a directionally solidified single-crystal structure. The turbine components can be manufactured with defects, including cracks, surface defects, imperfections and holes. These defects must be repaired by various repair processes for reliable, proper, and dependable performance of the turbines. Turbine components also develop defects during service throughout their lifetime. These service and use related defects may occur by wear, oxidation, and erosion. Such defects include cracks, surface defects, imperfections, and holes. These turbine component defects must be repaired for proper, dependable, and reliable operation of the turbine.
A previous defect repair method provided a repair material that is comparable in chemistry to the turbine component's parent superalloy. Also, the repair material in the previous defect repair method may have been provided with an oxidation resistance that is comparable, or even superior, to the turbine component's parent superalloy. The repair material was melted, and re-solidified to the turbine component at the defect site. The process was intended to provide an integral repaired structure, with a turbine defect site proximate the defect melting and re-solidifying with the repair material. Thus, repair material and the turbine component material formed a solid, one-piece repaired member.
For repair of a turbine component by a welding repair process, such as tungsten inert gas (TIG) welding, the repair material is often provided in the form of a repair material wire. A weld wire has been previously manufactured by powder metallurgy processes in conjunction with mechanically working to a wire form. Powder metallurgy processes often produce high volume fractions of strengthening precipitates, such as the intermetallic phase commonly referred to as gamma prime. The gamma prime precipitate material (.gamma.') in amounts up to about 70% by volume makes weld wire less ductile and hard to deform with low workability, and difficult to form into small diameter wires, and difficult to handle. The .gamma.'-containing material is difficult to mechanically deform at the temperatures commonly used for forming the weld wire, for example by a wire drawing process, is not ductile, and will not exhibit substantial plastic deformation to the point where the material will not easily bend. This type of low-ductility repair material is not well suited for further thermo-mechanical processing.
Complex multiple canning and hot extrusion processes have been attempted for producing weld wire, however the combination of these processes is an extremely expensive manufacturing process. For example, weld wire produced by the combination of multiple canning and hot extrusion processes may be up to ten times more in value than the raw metal itself.
Therefore, a repair material for turbine components that is relatively inexpensively produced, ductile, easy to therm-mechanically process, and readily capable of being mechanically deformed is needed.